Two=stage underground gasification of coal - with preliminary partial gasification of production area from array of boreholes

摘要

Process for underground gasification of solid fuels, e.g. coal, is as follows. (I) A channel is drilled along a fuel seam, and vertical holes drilled towards it: one enters the channel at one end, and the others are spaced along it but displaced to either side alternately. (II) The area around the channel is gasified in sections, each to the extent of 20% (max.) by injection of the required amt. of oxidant gas (pref. O2) from each offset hole in turn through the seam to the channel. (III) Gasification is completed by a gas flow along the channel. The average calorific value of the gas and deg. of gasification are increased. Fewer channels are needed for complete gasification of a seam, so that the costs are reduced.